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APPENDIX                                   30I

(2) also by passing a mixture of hydrogen cyanide and hydrogen
chloride into a phenol ether in presence of A1C13,
C6IIBOCII3 + HCN.IIC1 - Q-M4<         "     + IIC1.
The product is then hydrolysed with hydrochloric acid
/OCII3                          /OCII,
Q>n4<               +iiŤo = c;Hii4<:
XCII:NII       "                -CllO
(3) Grignard's reaction can also be used for preparing aromatic
aldehydes (p. 308).
The numerous reactions which benzaldehyde undergoes are
described in this preparation, and in some of the subsequent
ones (see Preps. 93-97).
On reduction, benzaldehyde yields, in addition to benzyl
alcohol, a pinacone known as liydrobenzoin,
c,,iiacoii                  cyr5cnoH
+ H3      -               I
QjIIgCOH                         CBII5CIIOII
a- and /3-Benzaldoximes.—The existence of two isomeric
benzaldoximes was first observed by Beckmann in 1889, vyho
explained their relation by a difference 'in structure.
C6H5CH:NOH              C6H5CH.NH
a-Benzaldoxime.                    jS-Benzaldoxime.
In the following year Hantzsch and Werner published their
theory, by which the greater number of isomeric oximes both of
aldehydes and ketones have found a satisfactory explanation.
These compounds were not structurally but stereo-isomeric, the
relation being similar to that which exists between fumaric, maleic
or mesaconic and citraconic acids (p. 265), or again between the
two diazotates of potassium (p. 283), and which may be
represented as follows :
C6H5.C.H                      C8H8.C.H
HO.N                                 N.OH
a-Benzaldoxime.                                  jS-Benzaldoxime.